The present invention relates to a methine compound useful as a photograhic material, medicine or the like, and to a pharmaceutical composition for treatment of cancer comprising the methine compound.
In the field of the photographic science, various methine compounds are described in, for example, U.S. Pat. Nos. 2,388,963, 2,454,629, 2,947,630, 3,979,213 and 3,796,733, French Patent Nos. 2,117,337 and 1,486,987, and West German Patent No. 2,140,323. These compounds are used as spectral sensitizing dyes. Among these, methine compounds which fall in rhodacyanine dyes usually have a low solubility, which causes a problem when they are incorporated into a photographic emulsion. For improving the solubility of these compounds, there is proposed a method wherein a hydroxyl group and methoxyethyl group are introduced into the molecular structure of each compound. Although such a method is disclosed in, for example, Japanese Patent Unexamined Published Application (hereinafter referred to as "J.P. KOKAI") Nos. Sho 63-228,145, 63-123,054 and 63-280,243, and Hei 3-168,634, 4-145,431 and 1-196,032, and European Patent No. 318,936, no satisfactory results have been obtained yet. Further, although the introduction of a sulfoalkyl group is also an ordinarily employed technique, this group seriously changes the charge of the compound, so that it is often that the essential properties of the compound cannot be maintained.
The medicinal effect of the methine compounds is expected in the medical and pharmaceutical fields, but the solubility is an important problem also in these fields and particularly in a medium having a high salt concentration such as blood in a living body, the precipitation or coagulation of such a compound is undesirable. For example, U.S. Pat. No. 5,360,803 and J.P. KOKAI Hei 6-80892 disclose compounds having a high solubility, but further improvement on the solubility is desired.
Thus, the solubility of the methine compounds is an important problem in both fields.